The invention relates to a multi-wavelength semiconductor light source and a process for producing the same, and particularly to a semiconductor integrated device for providing multi-wavelength light or white light using a plurality of semiconductor light emitting devices.
Methods have hitherto been proposed wherein lights from semiconductor light emitting devices, which respectively emit lights different from each other or one another in wavelength, are combined together through an optical fiber or an optical lens to provide a white light source or a multi-wavelength light source. For example, Japanese Patent Laid-Open No. 127424/1997 discloses a light source wherein a plurality of lights different from each other or one another in wavelength are combined using optical fibers and a multiplexer and the combined light is then made incident on a single optical fiber to provide white light.
FIG. 1 shows the construction of a conventional multi-wavelength semiconductor light source. This construction is disclosed in Japanese Patent Laid-Open No. 127424/1997. According to this construction, optical fibers 106 to 110 are connected respectively to LEDs (light emitting diodes) 101 to 105 which respectively emit lights different from one another in color (for example, LED 101 emits red light, LED 102 orange light, LED 103 yellow light, LED 104 green light, and LED 101 blue light). A multiplexer 111 is connected to respective ends of the optical fibers 106 to 110. An output optical fiber 112 is connected to the outgoing end of the multiplexer 111 and allows white light to exist therefrom.
In the construction shown in FIG. 1, the color lights emitted from LEDs 101 to 105 are passed through the optical fibers 106 to 110 and are gathered in the multiplexer 111, followed by multiplexing in the multiplexer 111. The multiplexing (color mixing) in the multiplexer 111 provides white light. This white light is passed through the output optical fiber 112 and is taken out of the output optical fiber 112.
Publication No. 512353/1997 of the Japanese Translation of International Patent Application proposes a color image formation system wherein lights from a plurality of light sources (semiconductor light emitting devices for three color lights, red light, green light, and blue light) are led to a deflection unit through an optical fiber to spacially combine the lights, and the combined light is further deflected by a deflecting mirror to form a two-dimensional or three-dimensional color image on a projection surface.
According to the conventional multi-wavelength semiconductor light sources, however, in the construction wherein a white light source or a multi-wavelength light source is used and light output from the light source is led to a multiplexer or a deflection unit through optical fibers, a large number of steps or a lot of time is necessary for coupling and matching between the plurality of semiconductor light emitting devices and the optical fibers or the waveguide. This leads to an increase in cost and, in addition, an increase In size of the system.
Accordingly, it is an object of the invention to provide a small-size and inexpensive multi-wavelength semiconductor light source that utilizes a plurality of semiconductor light emitting devices, which respectively emit lights different from each other or one another in wavelength, and can realize the formation of multi-wavelength light or white light, and a process for producing the same.
According to the first feature of the invention, a multi-wavelength semiconductor light source comprises: a substrate; a plurality of semiconductor light emitting devices provided on the substrate, for emitting respective lights different from each other or one another in wavelength; a plurality of optical waveguides provided on the substrate so that the optical waveguides in their one end are coupled respectively to the plurality of the semiconductor light emitting devices; and a multiplexer provided on the substrate so as to be coupled respectively to the other ends of the plurality of optical waveguides, for multiplexing lights output from the plurality of optical waveguides and outputting the multiplexed light.
According to this construction, all of a plurality of semiconductor light emitting devices, a plurality of optical waveguides coupled thereto, and a multiplexer coupled to the optical waveguides are integrally provided on an identical substrate to constitute a single device. This can eliminate the necessity of preparing separate components, components assembly step, and steps and works for matching or the like and thus can realize a reduction in size and a reduction in cost.
According to the second feature of the invention, a process for producing a multi-wavelength semiconductor light source comprises the steps of: forming a plurality of semiconductor light emitting devices, which each comprise a light emitting layer and a pair of cladding layers sandwiching the light emitting layer therebetween and emit respective lights different from each other or one another in wavelength, on a substrate by a method including etching or selective formation; and forming, on the substrate by a method including etching or selective formation, a plurality of optical waveguides, which each comprise a core layer and a pair of cladding layers sandwiching the core layer therebetween, the plurality of the optical waveguides in their one end being coupled respectively to the plurality of semiconductor light emitting devices, and a multiplexer coupled to the other ends of the plurality of optical waveguides.
According to this process, after the formation of a plurality of semiconductor light emitting devices on a substrate, a plurality of optical waveguides coupled to the semiconductor light emitting devices and a multiplexer coupled to the optical waveguides are formed onto the substrate. Accordingly, the plurality of semiconductor light emitting devices and the plurality of optical waveguides can be simultaneously provided on a single substrate. This can eliminate the necessity of preparing separate components, components assembly step, and steps and works for matching or the like and thus can realize a reduction in size and a reduction in cost.
According to the third feature of the invention, a process for producing a multi-wavelength semiconductor light source, comprising the steps of: forming a plurality of semiconductor light emitting devices, which each comprise a light emitting layer and a pair of cladding layers sandwiching the light emitting layer therebetween and emit respective lights different from each other or one another in wavelength, on a substrate by a method including etching or selective formation; and previously preparing a plurality of optical waveguides, which each comprise a core layer and a pair of cladding layers sandwiching the core layer therebetween, the plurality of the optical waveguides in their one end being to be coupled respectively to the plurality of semiconductor light emitting devices, and a multiplexer to be coupled to the other ends of the plurality of optical waveguides, and, after the formation of the plurality of semiconductor light emitting devices, mounting the plurality of optical waveguides and the multiplexer onto the substrate.
According to this process, after the formation of a plurality of semiconductor light emitting devices on a substrate, a plurality of optical waveguides coupled to the semiconductor light emitting devices and a multiplexer coupled to the optical waveguides are mounted onto the substrate. Accordingly, the plurality of semiconductor light emitting devices and the plurality of optical waveguides are simultaneously provided on a single substrate. This can eliminate the necessity of preparing separate components, components assembly step, and steps and works for matching or the like and thus can realize a reduction in size and a reduction in cost.